This is the age of information, where having constant access to critical data is the key to improved efficiency, productivity, and even profitability. Industrial networking capabilities have become the gateway to achieving the enterprise-wide communication and connectivity necessary to remain competitive in today’s marketplace. Implementing industrial networking solutions ensures that users have immediate access to critical production data, providing the highest level of control and visibility.

With the migration away from traditional point-to-point fieldbus, advanced networking architecture ensures connectivity, collaboration, and integration from the device level to enterprise business systems. To select the best solutions, it is important that manufacturers examine all options before implementation. For instance, users should analyze the performance capabilities and application suitability of protocols such as EtherNet/IP, Modbus TCP, and Profinet. Further, they should also understand the various environmental challenges, cabling types, and traffic issues to select the ideal networking solution for continuous, complete control over all production components.

Networking beyond office

Industrial Ethernet is based on the IEEE 802.3 standard. Though originally created for Ethernet found in the office environment, the standard has been modified for use in industrial automation. For Ethernet to be used in the industrial environment it must be adapted to withstand the environmental conditions that are not found in traditional installations. Most standard uses do not include exposure to extreme temperatures, humidity, vibration constant flexing, and noise that can be induced by drives, robots, or other equipment often found on the factory floor. Industrial applications have needs that are not associated with other types of applications

Before, Industrial Ethernet companies could not unite administrative, control-level, and device-level networks in one network infrastructure and were maintaining separate networks to support their factory floor and business operations. For example, the corporate IT network supports traditional administrative functions, while the control-level network connects control and monitoring devices and the device-level network links the controllers with the plant floor’s I/O devices. By combining the two functions onto one network, this allows for greater efficiency and control over the entire automation operation.

Industrial automation networks

As plants start moving to industrial networking solutions, it is important to consider some key factors, such as what network protocol to use, the network topology, and the overall environmental conditions the network will be subject to.

EtherNet/IP is a communication protocol that is supported by the ODVA for use in industrial automation and process control environments. It takes the Common Industrial Protocol (CIP) and implements it onto the foundation of Ethernet. CIP envelops a wide-ranging suite of messages and services for a variety of applications. EtherNet/IP provides users with a means to deploy standard Ethernet technology for industrial applications. EtherNet/IP can be used with star, tree, or line topology, but a switched topology is preferred in industrial applications. The use of managed switches allows the network to be configured to perform as close as possible to a real-time behavior, which is often required in industrial applications.

Profinet is the open Industrial Ethernet standard of Profibus and Profinet International (PI) for automation. It uses TCP/IP and IT standards and complements them with specific protocols and mechanisms to provide real-time performance capabilities. Profinet enables the integration of existing Fieldbus systems like Profinet, DeviceNet, and Interbus, without changes to existing equipment. Profinet can be used with star, tree, or line topology, but each layout needs to consider the overall requirements for the application.

Modbus TCP/IP is the Modbus RTU protocol with a TCP interface running on Ethernet. Modbus is managed by the Modbus-IDA User Organization. TCP/IP refers to Transmission Control Protocol and Internet Protocol, which provides the transmission channel for Modbus TCP/IP messaging. Modbus TCP/IP is used often in the industrial environment due to its ease of deployment and maintenance, and because it was developed specifically for industrial applications. Modbus TCP/IP can be used with star, tree, or line network topology and can be implemented with Ethernet technology that has been adapted for use in the industrial environment.

I personally agree that having access to data (process data as well as equipment health and instrument health etc.) is key to improved efficiency, productivity, and profitability since it can increase product quality, throughput, and process availability as well as reduce cost of operation & maintenance.

I also agree with digital communication networks are required to achieve this. I would personally also like to add that this digital networking has to start from the very “first meter”; at the sensors and actuators. That is, we cannot limit ourselves using point-to-point hardwired 4-20 mA and on/off signals for sensors and actuators. Instead we should go “digital everywhere” using digital communication networks also to connect transmitters, analyzers, control valve positioners, on/off valves, electric actuators and the like at the lowest level to get intelligence in every device. This enables not only real-time digital closed loop control, but also access to diagnostics etc. from the field instruments:http://www.eddl.org/DeviceManagement/Pages/DeviceDiagnostics.aspx

Therefore we have to be careful with the term “fieldbus” because there are two very distinct types of “fieldbus”: H1 fieldbus and H2 fieldbus.

“H2 fieldbus” is used at level 1-1/2 of the Purdue reference model to connect variable speed drives, motor starters, MCC, small package unit PLCs, and wireless gateways etc. to the main DCS control system. The fieldbus protocols traditionally used are DeviceNet, Modbus/RTU, and PROFIBUS which correspond to the new industrial Ethernet variants of these protocols: EtherNet/IP, Modbus/TCP, and PROFINET. Indeed there appears to be a migration away from the “H2” fieldbus towards their industrial Ethernet variants at this level.

However, “H1 fieldbus” is a different story. H1 is used at level 1 of the Purdue reference model. Industrial Ethernet is not taking the place of H1 fieldbus. This is why we have to explicitly make the difference between H2 and H1. H1 fieldbus is used for devices which are not available in an industrial Ethernet version. These are devices which traditionally use 4-20 mA and on/off signals, but the use of H1 digital commutation is on the rise. These include for example pressure transmitter, temperature transmitter, level transmitter, interface level transmitter, vortex flow meter, pH analyzer, conductivity analyzer, amperometric analyzer, control valve positioner, and on/off valve etc. As you can see, the devices connected by H1 fieldbus are quite different from those that connect using Industrial Ethernet. That is, H1 fieldbus and industrial Ethernet complement each other; together they cover all the devices around the plant. Indeed the H1 fieldbus at level 1 of the Purdue reference model enables access to more data from a massive amount of field instruments which in turn drives faster growth of industrial Ethernet at level 1-1/2 and above to get this data to the user.

Also, traditional fieldbus is not point-to-point. Traditional fieldbus is a bus topology. Point-to-point hardwiring is only used for 4-20 mA and on/off signals.